[Induction of heat-sensitive mutants of Junín virus using 5-fluorouracil]

This paper presents results concerning production, selection and isolation of conditionally lethal mutants of Junin virus. Two temperature sensitive (ts) mutants of Junin virus, XJCl3 strain, were isolated from a virus population that had been mutagenized with 5-Fluorouracil (5-FU). A study of the behaviour of wild-type virus over a range of temperature from 34 degrees C to 40 degrees C was done. In Vero cells, the initial cloned Junin virus stock gave very turbid plaques at 34 degrees C, more clear plaques at 37 degrees C and lytic pinpoint plaques at 40 degrees C. The efficiency of plaquing (ratio of plaques formed at 40 degrees C to plaques formed at 37 degrees C) in Vero cells was 0.86. Moreover, the wild-type virus had similar growth curves at 34, 37 or 40 degrees C in Vero cells. To study the 5-FU inhibition of Junin virus multiplication, Vero cell cultures were infected with approximately 0.6 PFU per cell and incubated in the presence of various doses of mutagen. After 24 hs of infection the yields were titrated. The mutagen inhibited virus multiplication in a dose-dependent manner. A concentration of 100 micrograms/ml, which reduced virus yields to 1% of that obtained in cultures lacking 5-FU, was chosen to select ts mutants. A rapid screening procedure based on the ability of Junin virus to develop cytopathic effects in Vero cells at 37 degrees C and 40 degrees C was used to identify potential ts mutants among 90 randomly picked plaque isolates obtained from virus grown at 34 degrees C during 24 hs in the presence of the mutagen.(ABSTRACT TRUNCATED AT 250 WORDS)